The Fukushima I Nuclear Power Plant, often referred to as Fukushima Dai-ichi, is a nuclear power plant located in the town of Okuma in the Futaba District of Fukushima Prefecture. With six separate units located on site with a combined power of 4.7 GW, Fukushima I is one of the 25 largest nuclear power stations in the world.

At 1630 JST (0730 GMT) on March 12, there was an explosion at the plant. At 1700 JST (0800 GMT), Fox News Channel reported the explosion and a plume of "white smoke" rising above the plant. At 1703 JST (0803 GMT) BBC News reported that Japan's NHK TV reported the explosion as "near" the plant, and that four workers were injured. Reuters is also reporting that NHK claims the explosion blew the entire outer structure off of the containment building of Unit 1. The video on BBC News shows both a close-up and distance view of the explosion.

The Guardian is reporting that NHK is advising residents of the Fukushima area "to stay inside, close doors and windows and turn off air conditioning. They have also been advised to cover their mouths with masks, towels or handkerchiefs" as well as not to drink tap water. Other news agencies have reported information on a definite explosion at the plant. At 1843 JST (0943 GMT) officials have confirmed that an explosion has occurred at the nuclear plant.

An increase in radiation levels has been confirmed following the explosion. "Fukushima Prefecture says a radiation level of 1,015 mircrosieverts [sic] per hour has been measured near the Fukushima Number 1 nuclear power station. One hour of exposure to this amount of radiation is equivalent to the permissible amount of radiation an ordinary person receives in one year"

At 1907 JST (1007 GMT) Reuters reported that the exclusion zone has been extended to 20 kilometres (12 mi) around the plant. BBC correspondent Nick Ravenscroft was stopped 60 kilometres (37 mi) from the plant by police.

At present officials do not believe that a Chernobyl-style disaster would occur, citing the differences between the lead up to the events at the Chernobyl Nuclear Power Plant and Fukushima I Nuclear Power Plant, and speculated that any nuclear material released during the incident would be confined to the grounds in and around the power plant.